Laser produced plasma (“LPP”) extreme ultraviolet light (“EUV”), e.g., at wavelengths below about 50 nm, using plasma source material targets in the form of a jet or droplet forming jet or droplets on demand comprising plasma formation material, e.g., lithium, tin, xenon, in pure form or alloy form (e.g., an alloy that is a liquid at desired temperatures) or mixed or dispersed with another material, e.g., a liquid. Delivering this target material to a desired plasma initiation site, e.g., at a focus of a collection optical element presents certain timing and control problems that applicants propose to address according to aspects of embodiments of the present invention.